The present invention relates to a quick-release coupler and, more particularly, to a quick-release coupler for securely coupling a bit to a pneumatic tool while allowing easy assembly.
FIG. 1 shows a conventional quick-release coupler 2 and a bit 1 coupled to the quick-release coupler 2. Bit 1 includes a driving end 12 for driving a screw or the like and a socket portion 11 having a coupling hole 111. A recessed portion 112 is formed in each of four side walls defining coupling hole 111. Quick-release coupler 2 includes a first end 21 for coupling with a hand-held tool such as a pneumatic tool (not shown) and a second end 22 having a receptacle 221 in which a spring 23 and a ball 24 are received. Ball 24 is biased by spring 23 such that an outermost portion 241 of ball 24 projects out of receptacle 221 and engages in one of recessed portions 112 of bit 1 when coupling hole 111 of bit 1 is coupled to second end 22 of quick-release coupler 2. Thus, bit 1 is locked on quick-release coupler 2 and can be driven when first end 21 of quick-release coupler 2 secured to the pneumatic tool rotates.
To remove bit 1 from quick-release coupler 2, a user generally grasps bit 1 and a handle of the pneumatic tool to pull them away from each other to make ball 24 retract into receptacle 221 to allow removal of bit 1 from quick-release coupler 2. However, it is sometimes difficult to remove bit 1 from quick-release coupler 2, particularly when ball 24 is jammed or the hands of the user are greasy. Moreover, bit 1 may be disengaged from quick-release coupler 2 during operation of the pneumatic tool when the resilience of spring 23 decreases.
U.S. Pat. No. 6,874,392 discloses a connector for a hand tool including a connector seat coupled to an operation member. The connector seat includes a main body, a movable rod, a positioning ball, and at least one spring. The main body includes a square receiving portion having a positioning hole that partially receives the positioning ball. The main body is movable relative to an operation seat of the operation member to retract the positioning ball into a receiving cavity of the movable rod, so that a socket can be mounted on and detached from the connector easily and conveniently, thereby saving the manual work. However, aligning the receiving cavity of the movable rod with the positioning hole of the square receiving portion of the main body while inserting the movable rod into the main body is not always easy, for the movable rod having circular cross sections may rotate relative to the main body also having circular cross sections.
Thus, a need exists for a quick-release coupler to allow secure attachment and easy removal of a bit to and from a hand-held tool while allowing easy assembly of the quick-release coupler.